1. Field of the Invention
The present invention relates to a motor control method performed by an apparatus.
2. Description of the Related Art
An ink jet recording apparatus and an image reading apparatus are provided with a motor control device that drives a motor.
The ink jet recording apparatus performs scanning by a recording head using driving force of the motor. The image reading apparatus performs scanning by a reading unit using the driving force of the motor.
The driving force of the motor includes a torque ripple (cogging torque), which is transmitted to a carriage via a timing belt. A moving speed of the carriage is controlled, for example, by using a previously prepared speed profile. However, the torque ripple causes speed variation in the moving speed. The torque ripple is generated at a certain period according to a structure of the motor. To remove an influence of the torque ripple, a feed forward control method is discussed in which a signal for decreasing the torque ripple is applied.
Japanese Patent Application Laid-Open No. 2006-42525 discusses a configuration in which a rectangular pulse which has a same period as that of the torque ripple is multiplied by a feedback controlled driving signal. It is further discussed that the rectangular pulse is applied at predetermined timing ahead of an opposite phase of the torque ripple.
Japanese Patent Application Laid-Open No. 2006-247997 describes that, when a load given to the motor is relatively large, the influence of cogging becomes relatively large. In Japanese Patent Application Laid-Open No. 2006-247997, thus, an amount of the load is measured and a voltage (duty value) applied to the motor to null the cogging is changed based on the amount of the load. Further, a correction value for changing the voltage and timing for applying the voltage are discussed. Furthermore, it is discussed that the speed variation is measured using an encoder and the above-described processing is performed until a measurement result falls below a threshold value.
However, since there are variations in ink jet recording apparatuses, it often takes a time to adjust the ink jet recording apparatus to reduce the torque ripple. For example, although Japanese Patent Application Laid-Open No. 2006-42525 discusses the timing for applying the rectangular pulse but no specific method for acquiring the timing. Japanese Patent Application Laid-Open No. 2006-247997 does not discuss a specific method for acquiring the timing for applying the voltage to null the cogging, either. As described above, both of the techniques need to perform scanning by a carriage many times to adjust the apparatus, thus taking time for adjustment.